As well known, yarns for industrial uses or shoe upper uses are generally used with yarns such as polyester, nylon, acryl resin and the like. The fabrics processed with the yarns disadvantageously have low durability, low abrasion resistance, and bad adhesion force, and accordingly, they are not adequate for high functional materials for shoe fabrics.
So as to solve such problems, currently, a coated yarn, which is made by coating thermoplastic resin onto the surface of yarn, is suggested to enhance the strength of yarn. The coated yarn is generally processed in such a manner that the thermoplastic resin such as PVC, PP or TPU is coated onto the yarn like polyester or nylon through dies of a general extruder.
In case of using the typical thermoplastic resin, however, it is hard to adjust the amount of thermoplastic resin coated, and particularly, it is very hard to coat a small amount of thermoplastic resin, so that the coated yarn has a thickness of more than 300 denier, thereby causing durability and abrasion resistance to be all deteriorated.
So as to solve the above-mentioned problems, the inventor has studied and developed a method for manufacturing coated yarn, compound for coated yarn, TPU coated yarn and so on from 2012 up to now, as suggested in Korean Patent Registration No. 10-1341054 (entitled ‘method for manufacturing coated yarn’ and dated on Dec. 13, 2013), Korean Patent Registration No. 10-1530149 (entitled ‘composition of compound for coated yarn having pore’ and dated on Jun. 19, 2015), Korean Patent Registration No. 10-1318135 (entitled ‘composition of thermoplastic polyurethane compound for coated yarn’ and dated on Oct. 15, 2013), Korean Patent Registration No. 10-1341055 (entitled ‘composition of thermoplastic polyurethane yarn and method for manufacturing the same’ and dated on Dec. 13, 2013).
According to the prior arts, coated yarns have excellent abrasion resistance, adhesion force, water resistance, and molding performance and further have relatively low thicknesses. In case of the coated yarns with cores like polyester or nylon, however, there is a limitation in their thickness, so that it is impossible to manufacture a coated yarn having a substantially low thickness, desirably, a thickness of 50 denier or under.
Further, the TPU coated yarns as suggested in the prior arts do not have high viscosity according to the characteristics of TPU, unlike polyester or nylon, so that a viscosity agent is necessarily used to perform gentle extrusion processing. In case of a mono-filament yarn having a relatively high thickness as a sole yarn unlike the TPU coated yarns, silica having a general size is used as the viscosity agent, but in case of a mono-filament yarn or multi-filament yarn having a thickness less than 50 denier, it should be made to a relatively low thickness, so that the silica having the general size cannot be used as the viscosity agent.